// slideToTop
var slideToTop = $("<div />");
slideToTop.html('<i class="fa fa-chevron-up"></i>');
slideToTop.css({
    position: 'fixed',
    bottom: '20px',
    right: '25px',
    width: '40px',
    height: '40px',
    color: '#eee',
    'font-size': '',
    'line-height': '40px',
    'text-align': 'center',
    'background-color': '#222d32',
    cursor: 'pointer',
    'border-radius': '5px',
    'z-index': '99999',
    opacity: '.7',
    'display': 'none'
});
slideToTop.on('mouseenter', function () {
    $(this).css('opacity', '1');
});
slideToTop.on('mouseout', function () {
    $(this).css('opacity', '.7');
});
$('.container').append(slideToTop);
$(window).scroll(function () {
    if ($(window).scrollTop() >= 150) {
        if (!$(slideToTop).is(':visible')) {
            $(slideToTop).fadeIn(500);
        }
    } else {
        $(slideToTop).fadeOut(500);
    }
});
$(slideToTop).click(function () {
    $("html,body").animate({		// firefox ie not support body, chrome support body. but found that new version chrome not support body too.
        scrollTop: 0
    }, 100);
});